A modern automobile is a technological marvel of substantial economic value. Often, it is protected by a security system designed to prevent theft and vandalism. The security system is just one of the optional equipment items present in a typical automobile or another vehicle. There are many others, for example, high-performance stereo sound reproduction systems, rear-seat entertainment systems, and navigation systems. These systems and similar entertainment, safety, and convenience items typically installed in cars and other vehicles (“installed equipment” or “installed components” hereinafter) can account for a considerable part of the total value of the vehicle. Left in the vehicle, the installed equipment is subject not only to the danger of being stolen together with the vehicle, but also to its own vagaries: for example, the installed equipment can be stolen from the vehicle, or the equipment can be abused while the vehicle is entrusted to a third party, such as a mechanic or a parking attendant.
Consider, for example, a high-power audio amplifier. Its cost can be in many hundreds or thousands of dollars, and much effort can be spent on its installation. Obviously, it presents a tempting target to a potential thief. Furthermore, the power produced by the amplifier can damage the loudspeakers of the vehicle under some circumstances. The vehicle's owner may not want to allow access to the amplifier and to the rest of the sound reproduction system when leaving the vehicle with a parking attendant or an auto mechanic. For these and other reasons, some amplifiers have a mode in which they are non-functional. When locked in this mode, the amplifier cannot be used in the vehicle where it was originally installed or in another environment, without a key used to unlock it. Unfortunately, inserting and removing a physical key, such as a key that includes an electronic memory with burned-in code, is inconvenient because the amplifier is likely to be located in a trunk or another location that is not conveniently accessible. A need thus exists for a convenient method and apparatus to lock and unlock installed equipment electronically.
Moreover, the installed equipment may need to be configured, periodically monitored, and diagnosed. The stereo amplifier discussed above, for example, can be a rather sophisticated piece of audio equipment with programmable configuration and diagnostic features. One example of such features is the availability of programmable gain adjustment and gain adjustment lockout mechanisms. Another example is the programmability of turn-on delay. Yet another example is the availability of self-diagnostic information stored within the amplifier. Typically, access to such configuration and diagnostic features requires specialized equipment used by dealers and installers of electronic equipment. It would be desirable to provide at least limited access to these features to the end-user, and to dealers and installers without the specialized equipment. A need thus exists for a method and apparatus that would allow convenient access to configuration and diagnostic features of the installed equipment.